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Pennsylvania Railroad class I1s

From Wikipedia, the free encyclopedia

Pennsylvania Railroad I1s
PRR I1s prepares to leave the docks at Cleveland, Ohio with a trainload of iron ore in May, 1943.
Type and origin
Power typeSteam
BuilderPennsylvania Railroad's Altoona Shops (123); Baldwin Locomotive Works (475)
Build date1916–1923
Total produced598
 • Whyte2-10-0
Gauge4 ft 8+12 in (1,435 mm)
Driver dia.62 in (1,575 mm)
Axle load72,600 lb (32,900 kilograms; 32.9 metric tons)
Adhesive weight352,500 lb (159,900 kilograms; 159.9 metric tons)
Loco weight386,100 lb (175,100 kilograms; 175.1 metric tons)
Tender weight204,700 lb (92,900 kilograms; 92.9 metric tons)
Total weight590,800 lb (268,000 kilograms; 268.0 metric tons)
Fuel capacity18.7 t (18.4 long tons; 20.6 short tons)
Water cap10,300 US gal (39,000 l; 8,600 imp gal)
 • Firegrate area
69.9 sq ft (6.49 m2)
Boiler pressure250 psi (1.7 MPa)
Feedwater heaterWorthington BL
Cylinder size30+12 in × 32 in (775 mm × 813 mm)
bore × stroke
Performance figures
Maximum speed50 mph (80 km/h)
Tractive effortI1s—96,000 lbf (430 kN)
I1sa—102,027 lbf (453.84 kN)
93,625 lbf (416.46 kN) @78% cutoff
OperatorsPennsylvania Railroad
PreservedOne - #4483
DispositionPRR 4483 on display, remainder scrapped

The Pennsylvania Railroad's class I1s steam locomotives were the largest class of 2-10-0 "Decapods" in the United States, with 598 built 1916–1923 (Altoona: 123, Baldwin: 475). They were the dominant freight locomotive on the system until World War II, and they remained in service until the end of PRR steam in 1957. Nicknames for the type included Decs and Hippos, the latter due to the large boiler. Unlike smaller 2-10-0s that preceded them, the I1s design was huge, taking advantage of the PRR's heavy trackage and high allowed axle load, with a wide, free-steaming boiler. Large cylinders enabled the I1s to apply that power to the rails. However, the large boiler limited the size of the driving wheels, which made it impossible to mount counterweights large enough to balance the piston thrusts. As a result, they were hard riding at anything but low speeds and prone to slipping, and not popular with crews.[1] Their power was undeniable, with one author describing them as "the holy terror of the PRR".

Subclass I1sa increased maximum steam cut-off to admit steam for 78% of the piston stroke (rather than the original 50%), boosting low speed tractive effort from 90,000 to 96,000 pounds-force (400 to 430 kN). There was no obvious external difference except for a revised builders' plate (and of course the revised combination lever). I1s locomotives were converted to I1sa during major overhauls; eventually 489 were converted while 109 remained as built.

In 1923 PRR put engine 4358 on the Altoona test plant. The tests below were all stoker fired.

  • In two hours at 7.12 miles per hour (11.46 km/h) it consumed 8,129 pounds (3,687 kg) of coal (13,398 BTU/lb or 5,760 kJ/kg) and averaged 71,993 pounds (32,655 kg) of tractive effort at the driver rims, corresponding to 6.4% thermal efficiency.
  • In one hour at 14.24 miles per hour (22.92 km/h) it consumed 6,809 pounds (3,089 kg) of coal (12,682 BTU/lb or 5,452 kJ/kg) and averaged 63,263 pounds (28,696 kg) tractive effort, or 7.1% efficiency.
  • At 22.02 miles per hour (35.44 km/h) (40% cutoff, so not a maximum effort) it consumed 7,000 lb/h (3,200 kg/h) of 13,039 BTU/lb (5,606 kJ/kg) coal and averaged 43,515 pounds (19,738 kg) TE, for 7.1% efficiency.
  • At 21.36 miles per hour (34.38 km/h) at 50% cutoff it consumed 5,230 pounds (2,370 kg) of 13,372 BTU/lb (5,749 kJ/kg) coal in 30 minutes averaging 51,409 pounds (23,319 kg) TE, for an efficiency of just under 5.4%. The I1's whistle is mostly a PRR banshee whistle.


Of the nearly 600 class I1 locomotives built for the Pennsy, a sole example, #4483, survived the scrapper's torch. The locomotive was retired in August of 1957. Following then Chief of Motive Power Hal T. Cover's instructions, the railroad moved the engine to its roundhouse in Northumberland, PA, along with several other retired steam locomotives labeled for preservation. There the engine sat until 1963, when the PRR sold it to the Westinghouse Air Brake Company (WABCO) and moved the engine to Wilmerding, PA. WABCO had originally sought a railroad-themed display for its headquarters to commemorate its heritage of supplying air brakes to America's railroads. #4483 saw little maintenance during its life as a display piece for the company and its condition deteriorated significantly, although the boiler's asbestos cladding was removed.[2]

By 1982, the company had grown tired of the locomotive on its front lawn. The Western New York Railway Historical Society acquired #4483 and moved the engine to Hamburg, NY, where it resides today, receiving occasional maintenance. Currently, the organization hopes to move the locomotive to the Heritage Discovery Center in Buffalo, NY, where the engine will sit on public display protected from the elements.[2]



  1. ^
  2. ^ a b "PRR #4483". Western New York Railway Historical Society. February 7, 2017. Archived from the original on October 17, 2018. Retrieved September 15, 2019.

External links

This page was last edited on 4 May 2021, at 00:20
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